Owing to the increasing demand for petrochemical products from developing countries such as China, in the recent petrochemical product market, the stable supply of olefins, particularly light olefins which are used as a raw material for various petrochemical products has become an issue in this market.
Among those light olefins, a demand for and value of N-butene and 1,3-butadiene which serve as a raw material for various synthetic rubber and copolymer products are particularly increasing, and the methods for producing them may be largely classified by naphtha cracking, direct dehydrogenation of n-butane or n-butene, or oxidative dehydrogenation of n-butane or n-butene. Among them, the naphtha cracking process affords most of n-butene and 1,3-butadiene supply in the market, reaching to approximately 90% of supply n-butene and 1,3-butadiene. However, a naphtha cracking process has a disadvantage such that it has a general purpose for producing basic petrochemical feedstock such as ethylene, propylene, etc., not a process dedicated to the production of n-butene and 1,3-butadiene. In the meantime, new establishment or expansion of naphtha cracking center only for the purpose of increasing the production of n-butene and 1,3-butadiene cannot be made without any particular plan, and if so, it would cause a further problem of surplus production of other basic petrochemical feedstock other than n-butene and 1,3-butadiene. Moreover, with an increasing demand for ethylene and propylene, new establishment and operation regarding a naphtha cracking process tends to be rather focused to increase in production yield of ethylene and propylene, and thus modified as a process using light hydrocarbons such as ethane, propane, etc. as a raw material which can result in high production yield for basic petrochemical feedstock such as ethylene, propylene and the like, although its yield for C4 mixtures is low. In addition to that, with the continuous price increase in raw materials for C4 production, the proportion of a process for obtaining C4 in the naphtha cracking process is relatively reduced. In consequence, with those obstacles as above, it is getting more difficult to secure C4 mixtures, particularly n-butene and 1,3-butadiene through a naphtha cracking process.
As the foregoing description, although n-butene and 1,3-butadiene supply majorly depend on a naphtha cracking process, this process cannot be an effective way to resolve the imbalance between supply and demand caused by recent increased demand in n-butene and 1,3-butadiene, based on the many reasons as above. In this circumstance, a dehydrogenation reaction in which hydrogens are removed from n-butane or n-butene thus obtaining n-butene and 1,3-butadiene, is recently getting a great attention as an alternative process which can rapidly cope with the increasing demand for n-butene and 1,3-butadiene in market, and thus other related studies have been vigorously made. [N. Kijima, M. Toba, Y. Yoshimura, Catal. Lett., vol. 127, p. 63 (2009); I. C. Marcu, I. Sandulescu, J. M. M. Millet, Appl. Catal. A, vol. 227, p. 309 (2002); L. M. Madeira, J. M. Herrmann, F. G. Freire, M. F. Portela, F. J. Maldonado, Appl. Catal. A, vol. 158, p. 243 (1997); A. A. Lemonidou, G. J. Tjatjopoulos, I. A. Vasalos, Catal. Today, vol. 45, p. 65 (1998)].
The dehydrogenation reaction of n-butane can be classified into direct dehydrogenation and oxidative dehydrogenation, wherein the direct dehydrogenation reaction of n-butane is highly exothermic and thus a thermodynamically disadvantageous reaction since hydrogen should be directly detached from n-butane as well as requires great energy consumption to satisfy the high-temperature reaction condition. For carrying out direct dehydrogenation, used are precious metal catalysts such as platinum or palladium, which require a reactivation process owing to their short lifetime in most cases, therefore the direct dehydrogenation is not considered to be a suitable commercial process for producing 1,3-butadiene. [A. Wu, C. A. Frake, U.S. Pat. No. 6,433,241 B2 (2002); A. Wu, C. A. Frake, U.S. Pat. No. 6,187,984 (2001)].
On the contrary, unlike the direct dehydrogenation, the oxidative dehydrogenation of n-butane, wherein n-butane and oxygen reacts to produce n-butene and water, and thus obtained n-butene further reacts with oxygen to produce 1,3-butadiene and water, is thermodynamically advantageous as compared to the direct dehydrogenation reaction of n-butane since an endothermic reaction turns to an exothermic reaction with the generation of water after the reaction, wherein water generated from the catalyst reaction may have a role of a heat sink which can prevent rapid temperature changes in the catalyst layer. In this respect, the oxidative dehydrogenation process of n-butane can be operated under process conditions more advantageous than those of the direct dehydrogenation process, and therefore, upon the development of a catalyst process for producing n-butene and 1,3-butadiene with high efficiency, this process can be a method which can cope with the recent increase in n-butane and 1,3-butadiene in the recent market.
As described above, the oxidative dehydrogenation of n-butane for producing n-butene and 1,3-butadiene includes a reaction between n-butane and oxygen to produce water and n-butene which reacts with oxygen in the same way again to produce water and 1,3-butadiene. From the above description, although this reaction has many advantages over the direct dehydrogenation of n-butane in many ways such as a thermodynamic aspect which makes possible to produce n-butene and 1,3-butadiene with a high yield, under mild reaction conditions, it has a drawback that many side reactions such as highly oxidative reactions which involve generation of carbon monoxide or carbon dioxide owing to the use of oxygen as a reactant.
Therefore, the most crucial technical point in the oxidative dehydrogenation process of n-butane is to achieve a catalyst with highly increased selectivity to n-butene and 1,3-butadiene by preventing side reactions such as complete-oxidative reactions, while achieving the conversion of n-butane to the maximum. Although the reaction mechanism of the oxidative dehydrogenation of n-butane has not yet been exactly known, it is reported that, as a first step, by the reaction of the active site of metal in the catalyst and lattice oxygen, hydrogen is detached from n-butane adsorbed in the solid catalyst and simultaneously a redox reaction of a catalyst itself and loss of lattice oxygen occur, and therefore complex oxide catalysts containing transition metal ions which may be in various oxidation states are essential to this oxidative dehydrogenation reaction [H. H. Kung, Ind. Eng. Chem. Prod. Res. Dev., vol. 25, p. 171 (1986)].
So far, catalysts known to effectively produce n-butene and 1,3-butadiene through oxidative dehydrogenation of n-butane are magnesium orthovanadate catalysts [M. A. Chaar, D. Partel, H. H. Kung, J. Catal., vol. 105, p. 483 (1987); M. A. Chaar, D. Partel, H. H. Kung, J. Catal., vol. 109, p. 463 (1988); O. S. Owen, H. H. Kung, J. Mol. Catal., vol. 79, p. 265 (1993); A. A. Lemonidou, G. J. Tjatjopoulos, I. A. Vasalos, Catal. Today, vol. 45, p. 65 (1998); Korean patent application No. 10-2011-0021037 (2011) [by Song In Kyu, Lee Ho Won, You Yoen Sik, Jo Young Jin, Lee Jin Suck, Jang Ho Sik; vanadium oxide catalysts [A. F. Dickason, U.S. Pat. No. 3,914,332 (1975); M. E. Harlin, V. M. Niemi, A. O. I. Krause, J. Catal. Vol. 195, p. 67 (2000); V. M. Murgia, E. M. F. Torres, J. C. Gottifredi, E. L. Sham, Appl. Catal. A, vol. 312, p. 134 (2006)]; pyrophosphate catalysts [I. C. Marcu, I. Sandulescu, J. M. M. Millet, Appl. Catal. A, vol. 227, p. 309 (2002); F. Urian, I. C. Marcu, I. Sandulescu, Catal. Commun., vol. 9, p. 2403 (2008)], ferrite catalysts[H. Armendariz, J. A. Toledo, G. Aguilar-Rios, M. A. Valenzuela, P. Salas, A. Cabral, H. Jimenez, I. Schifter, J. Mol. Catal., vol. 92, p. 325 (1994); L. Bajars, L. J. Croce, U.S. Pat. No. 3,303,234 (1967)] and the like.
The characteristic feature shared by the above complex oxide catalysts is the presence of transition metals, which are necessary for transition of electrons between the catalyst and n-butane via the redox reaction of the catalyst as explained above [H. H. Kung, Ind. Eng. Chem. Prod. Res. Dev., vol. 25, p. 171 (1986)]. The catalysts can carry out the oxidative dehydrogenation of n-butane by incorporating metals which can be oxidized and reduced such as, for example, vanadium, iron, nickel and titanium, etc., and among them, particularly, magnesium o-vanadate catalysts which contain vanadium are known to have high activity, based on which it is considered for the redox potential of vanadium metal to be suitable for the oxidative dehydrogenation of n-butane [M. A. Chaar, D. Partel, H. H. Kung, J. Catal., vol. 105, p. 483 (1987); M. A. Chaar, D. Partel, H. H. Kung, J. Catal., vol. 109, p. 463 (1988)].
Magnesium o-vanadate catalysts are generally produced to be the form in which the active phase of Mg3(VO4)2 is supported by a separate metal oxide. It is reported that when magnesium o-vanadate catalysts are not supported, the activity is lower than that of supported magnesium o-vanadate.
For example, some results of oxidative dehydrogenation of n-butane by using unsupported magnesium o-vanadate catalysts have been reported in conventional patents and literatures, specifically, for example, 11.5% of n-butane conversion rate, 6.7% of dehydrogenation product yield under the conditions of 540° C. and the feed composition ratio of n-butane:oxygen:helium=4:8:88 [O. S. Owen, H. H. Kung, J. Mol. Catal., vol. 79, p. 265 (1993)], and 5.7% dehydrogenation product yield under the conditions of 540° C. and the feed composition ratio of n-butane:oxygen:helium=5:10:85 [A. A. Lemonidou, G. J. Tjatjopoulos, I. A. Vasalos, Catal. Today, vol. 45, p. 65 (1998)]. When magnesium o-vanadate catalysts are supported, the activity can be more improved [A. A. Lemonidou, G. J. Tjatjopoulos, I. A. Vasalos, Catal. Today, vol. 45, p. 65 (1998)]. Specifically, magnesia supported magnesium o-vanadate catalysts obtained by supporting vanadium to excessive amount of magnesia and their excellent activity for the oxidative dehydrogenation of n-butane have been reported [M. A. Chaar, D. Partel, H. H. Kung, J. Catal., vol. 109, p. 463 (1988); O. S. Owen, H. H. Kung, J. Mol. Catal., vol. 79, p. 265 (1993); A. A. Lemonidou, G. J. Tjatjopoulos, I. A. Vasalos, Catal. Today, vol. 45, p. 65 (1998)]. Specifically, it was reported that when the oxidative dehydrogenation of n-butane under the conditions of 600° C. and the composition ratio of n-butane:oxygen:nitrogen of 2:1:97 was conducted by using a magnesia-supported magnesium o-vanadate catalyst obtained by mixing magnesium hydroxide with a mixed aqueous solution of ammonium vanadate and ammonia with the ratio of Mg to V of 6:1, it resulted in 30.4% of n-butane conversion rate, 70.6% of dehydrogenation product selectivity and 21.5% of dehydrogenation product yield [N. Kijima, M. Toba, Y. Yoshimura, Catal. Lett., vol. 127, p. 63 (2009)], and when the oxidative dehydrogenation of n-butane under the conditions of 540° C. and the composition ratio of n-butane:oxygen:helium of 5:10:85 was conducted by using a magnesia-supported magnesium o-vanadate catalyst, it resulted in the yield of 22.8% [A. A. Lemonidou, G. J. Tjatjopoulos, I. A. Vasalos, Catal. Today, vol. 45, p. 65 (1998)]. Further, also reported were the results of 35.4% of n-butane conversion rate and 18.1% of dehydrogenation product yield, by using a magnesia-supported magnesium o-vanadate catalyst under the higher oxygen conditions wherein the composition ratio of n-butane:oxygen:helium=5:20:75, as compared to said reactions of the prior arts [J. M. Lopez Nieto, A. Dejoz, M. J. Vazquez, W. O'Leary, J. Cunnungham, Catal. Today, vol. 40, p. 215 (1998)].
Further reported was a method for using magnesium o-vanadate catalyst which makes possible to increase the activity for the oxidative dehydrogenation of n-butane by mixing additives to magnesia-supported magnesium o-vanadate catalyst so as to obtain products from the dehydrogenation, n-butene and 1,3-butadiene with high yield in the literature of [D. Bhattacharyya, S. K. Bej, M. S. Rao, Appl. Catal. A, vol. 87, p. 29 (1992)], wherein the dehydrogenation was carried out under the conditions of 570° C., a composition ratio of n-butane:oxygen:nitrogen of 4:8:88 by using 25 wt % of a magnesia-supported magnesium o-vanadate catalyst further mixed with titanium oxide and chromium oxide, resulting in 54.0% of n-butane conversion rate and 33.8% of dehydrogenation product yield.
Although it is possible to the desired reaction product n-butene and 1,3-butadiene with a very high yield, by using said magnesia-supported magnesium o-vanadate catalyst in the oxidative dehydrogenation of n-butane, its commercial application is limited. This is because that although the magnesia-supported magnesium o-vanadate catalyst has high activity, the redox reaction of the catalyst which should be reversible is carried out partly irreversible, [N. Kijima, M. Toba, Y. Yoshimura, Catal. Lett., vol. 127, p. 63 (2009)], thereby failing to maintaining the high catalyst activity for a long time.
To solve such problem of said prior art, the present inventors established a method for producing a thermally- and chemically-stable magnesium o-vanadate catalyst supported by a zirconia or magnesia-zirconia complex carrier, without problems such as a decrease in catalyst activity with the lapse of time or low catalyst activity of other vanadium oxide catalysts, and also developed a catalyst reaction process for preparing n-butene and 1,3-butadiene at a high yield in a stable way by using thus prepared catalyst [by Song In Kyu, Lee Ho Won, You Yoen Sik, Jo Young Jin, Lee Jin Suck, Jang Ho Sik, Korean Patent application No. 10-2011-0021037 (2011); Song In Kyu, Lee Ho Won, You Yoen Sik, Jo Young Jin, Lee Jin Suck, Jang Ho Sik, Korean Patent application No. 10-2011-0051293 (2011)]. In the above-mentioned prior patent applications, the present inventors developed a method for preparing a magnesium o-vanadate catalyst supported by the magnesia-zirconia complex carrier which comprises magnesia and zirconia at a certain ratio, which can obtain n-butene and 1,3-butadiene at a high yield in a stable way through the oxidative dehydrogenation of n-butane without any hint of catalyst inactivation, in which the method comprises: preparing a zirconia carrier for a catalyst for the oxidative dehydrogenation of n-butane by a gel-oxalate method; then supporting magnesium and vanadium thereto, thus obtaining a zirconia carrier or a magnesia-zirconia complex carrier; and finally preparing a magnesium o-vanadate catalyst supported by the zirconia carrier or magnesia-zirconia complex carrier.
However, over the above-mentioned prior arts and patent applications, further improvement regarding the activity in the oxidative dehydrogenation of n-butane and the reproducibility of the catalyst preparation is still needed in this field of art.